1. Field of the Invention
This invention relates to the use of the bovine prolactin promoter to control the expression of heterologous genes in transgenic animals or in cell or tissue culture.
2. Information Disclosure Statement
Prolactin is a hormone secreted by the anterior pituitary. Its biological activities include maintenance of lactation after birth and osmoregulation. Prolactin is required for spermatogenesis in rodents, but its role in that process in humans is unclear. Prolactin is produced by a wide variety of animals, including mammals such as humans, monkeys, cows, pigs, sheep, and rats, and other vertebrates such as fish and birds.
The genes encoding several animal prolactins have been sequenced. Cooke, et al., J. Biol. Chem., 256(8): 4007 (1981) (human); Cooke, et al., J. Biol Chem., 255(13): 6502 (1980)(rat); Nilson et al., Nucleic Acids Res., 8(7): 1561 (1980) (bovine); Kuwana, EP Appl 201,882 (Nov. 20, 1986)(fish).
In particular, the 5' flanking region (promoter) of the bovine prolactin gene, has been characterized. Camper et al., DNA, 3:237-249 (1984); Camper, et al., J. Biol. Chem., 260: 12246-51 (1985); Nilson, et al., Nucl. Acids Res., 8: 1561-73 (1980) ; Sasavage, et al., J. Biol. Chem., 257: 678-81 (1982). A region of high homology among the rat, human and bovine promoters has been noted, Camper, et al. (1985). Other homologies are noted in Rottman, et al., in MOLECULAR AND CELLULAR ASPECTS REPRODUCTION 281-299 (Dhindsa and Bahl, eds., 1986).
Expression of the prolactin gene is regulated by many factors, including epidermal growth factor (EGF), thyrotropin releasing hormone (TRH), glucocorticoids, vasoactive intestinal polypeptide, cAMP, ergot alkaloids, dopamine, estrogen, and calcium. See, e.g., Dannies, Ch. 7, "Prolactin", in Handbook of Neurochemistry, Vol. 8, pp. 159-174 (1985). Camper et al. (1985) established that the DNA sequences necessary for regulation by EGF, TRH and dexamethasone lie within the 250 nucleotides immediately flanking the 5' end of the structural gene.
The bovine prolactin (bPRL) promoter (1 Kb fragment) has been fused to a "promoterless" chloramphenicol acetyltransferase (CAT) gene. Camper et al. (1985). Transcription of the CAT gene driven by the bPRL promoter was observed in GH.sub.3 cells (a rat pituitary tumor cell line), but not in COS-1 (monkey kidney) or HeLa cells. Transcription was stimulated by EGF and TRH, and inhibited by dexamethasone, a synthetic glucocorticoid hormone. See also Sakai, et al., Abstract, "The Glucocorticoid Receptor Mediates Repression of Transcriptional Enchancers from the Bovine Prolactin Gene," in Steroid Hormone Action, UCLA Winter Symposium (January 1987).
Similarly, Nelson, et al., Nature, 322:557 (1986) reports the coupling of the rat prolactin promoter to a heterologous gene, and the expression of the hybrid gene in tissue culture.
Palmiter and Brinster, Ann. Rev. Genetics, 20: 465-499 (1986) review experiments with gene transfer into the germ-line cells of mice and with gene expression in transgenic mice. Table 4 refers to expression of a "prolactin/SV40 early region" transgene in pituitary (lactotroph) cells of transgenic mice. The researcher (Rosenfeld) apparently observed tumorigenesis in the lactotroph cells.
No admission is made that any of the foregoing references constitute prior art, that work described in the publications of others was in fact performed as described, or that the publication dates given in the publications are exact. Applicants do not necessarily concur with the opinions expressed in the references.